Crush Oreo cookies in a food processor or blender until really fine.
Melt butter in a glass 9-inch deep-dish pie plate in the microwave. Add the fine cookie crumbs and mix together until evenly combined. Use the bottom of a measuring cup to press the crumbs to the bottom and sides of the pie dish. Place crust in the fridge while working on the pudding.
In a medium sauce pan, add milk and semi-sweet chocolate chips. Heat mixture while stirring over high heat until chocolate melts; about 1-2 minutes.
Place egg yolks and sugar into a medium-sized mixing bowl. Whisk together with a fork until pale yellow. Add cornstarch, salt, and vanilla. Mix well.
Pour warm chocolate mixture into the egg mixture, SLOWLY, whisking as you go so you don't curdle the eggs. Pour the mixture back into the saucepan and place it onto the stovetop.
Over medium-high heat, bring mixture to a boil, whisking constantly until thick. (Happens suddenly when it reaches a boil.) Remove from heat and whisk vigorously for 1-2 minutes until creamy and smooth.
Pour pudding into the pie crust. (*If you don't have a deep pie dish, you can save any extra pudding in small cups in the fridge.) Cover with plastic wrap, pressing the wrap gently onto the top of the pudding. (This helps the pudding from creating a film on top.)
Cool to room temperature, then refrigerate the pie for a minimum of 4 hours. (Overnight works best.)
Make the whipped cream: Pour heavy cream into a stand mixer with the whisk attachment. Beat until slightly thick, then add sugar and vanilla. Continue beating until medium-stiff peaks. Spread over pie.
Use a vegetable peeler to cut chocolate shavings with the large chocolate bar over the whole pie. Serve and enjoy! Refrigerate leftovers. Can be made up to 24 hours in advance.